hard disk

My name is amr adel and I have an acer extensa 4620,it has an 80 GB HDD into two partions one of them is for system so I left it alone.And one for Data , the data one is 32 GB I filled 30 GB , anyway this morning the bar next to Partion was blue , so I tried to copy this data into an external Hard Disk But in the middle of copying , accidentally the USB was unplugged , and then it didn't turn back blue again what can I do Please Help Thanx. and what does this bar mean ?